Gerald Baxter, prosecuting, told the court that in the run up to the siege, McDonald had made threats he was going to do "something spectacular" in order to publicise a number of grievances he had.

He said he planned to smash up works of art in the Tate Gallery with a sledge hammer.

McDonald's mental illness had made him convinced that the police were stalking him and he believed he was being persecuted by the government, health care professionals and solicitors.

He had built a number of placards outside his home detailing his conspiracy theories.

The court heard McDonald had made a number of phone calls demanding a meeting at his home with the Chief Constable, a social worker and Dr Higgo.

At 11am on March 6, the doctor went to meet him with outreach manager Vincent Farrell.

McDonald had set up a video camera to record the meeting but when the doctors said they would not stay for the six hours he demanded, he became agitated, stormed out the room and returned with a pistol.

Mr Farrell escaped, but Dr Higgo was held hostage in an upstairs room while McDonald either pointed the gun at him or kept it within easy reach.

McDonald smoked around 20 cannabis cigarettes during the siege.

Mr Baxter said the doctor told police negotiator she feared for his life as McDonald had threatened to kill him if police stormed the house.

At 4.30am McDonald threw his weapon on to the street and he surrendered at 10am.

Andrew Menary QC, defending, told the court McDonald held the doctor hostage because he wanted a platform to air his grievances.

He said that the siege had not been planned and he did not intend to endanger Mr Higgo's life.

He said: "This was not a kidnap situation, Mr McDonald is not an evil person. It was born of frustration because of his real or imagined concerns.

"Mr McDonald does not accept he is suffering from a mental illness."

The court heard that in 1988, McDonald was jailed for 10 years for shooting brothers James and Martin Dykstra.

Because McDonald had already been convicted of two serious offences a life sentence was mandatory.

But it is likely he will be detained at Ashworth High Security Hospital.

Judge Henry Globe QC, the recorder of Liverpool, recommended McDonald serves a minimum of three years and three months.